This is how to repair holes and cracks in your boat!

Is your boat damaged and do you want to repair it easily? In this article we explain step by step how you can repair cracks, scratches or holes in your boat hull (below the waterline). In addition to this step-by-step plan, you will also read all about the necessary materials in this article. This way you get started efficiently and with the right materials!
 

Do you have questions about repairs to your boat after reading this informative article? Or do you have doubts about the (quantity of) suitable materials? Please do not hesitate to contact our specialists for tailored advice!

Step-by-step plan for boat repair (below the waterline)

In the video below, product specialist Arne shows how to easily carry out a polyester repair. Here he uses the Polyester repair kit. We wrote down all the steps so you can read it again later.

Step 1. Map the damage

Before you start boat repair, it is first important to take stock of the damage. Check carefully where the damage is and what the damage is. Think of cracks, scratches or holes from removed equipment (such as a log or depth gauge).

After you have inventoried all the repairs, you can calculate how much material you will need to carry out the repairs.

In this article we discuss repairing damage to the underwater hull. For repairs to the superstructure, please read the article: Repairing the superstructure.

Step 2. Chamfer off holes, cracks and scratches

Supplies:

Chamfer cracks and scratches with an 8:1 bevel. For minor repairs you can use a sander. An angle grinder with flap disc is indispensable for major repairs. 

Unnecessary holes should also be chamfered. In many cases we recommend carrying out the repair from both the inside and outside. It is often decided to first bevel the outside to approximately 2/3 of the hull thickness. Once the outside has been repaired, you need to grind out and repair the inside.

After grinding, check whether the cracks are not deeper than expected. Wet the sanding area and wipe it dry again. In a crack the water will remain longer and become visible again. Grind out these cracks even deeper.

Finally, make a plug from, for example, a piece of leftover plywood covered with tape or cardboard. This is how you bridge the gaps of equipment.

Tip: it is also possible to use a fibre disc and adapter. This is a quick and cheap solution. 

Step 3. Repair damage using polyester and glass fabric

Supplies:

Tip: with the Polyester repair kit, you immediately have everything you need to carry out a polyester repair!

In this step, we are going to laminate holes and cracks with polyester laminating resin combined with glass fibre. Always clean and dust the surface before you start laminating. In addition, make sure you always wear the right protective equipment while working with polyester. Always wear covering clothing, a suitable fume mask and nitrile gloves.

Tip: use the Polyester safety kit with all the necessary protective equipment.

Repairing holes
Add approximately 2% MEKP hardener to the polyester laminating resin and mix well in a clean mixing cup. While mixing, the polyester resin will slowly change colour.

Once you have mixed the polyester resin well, apply a layer of resin to the surface. Apply enough fibreglass chopped strand mat around the hole. Do this from large to small and vent the surface after each layer with a vent roller. After each layer of fibreglass, apply another layer of polyester resin. Work layer by layer until the fabric is level with the surrounding surface. Now let the polyester resin harden completely. 

For holes that are completely through the hull, once cured on the inside, the temporary plug can be removed and the spot can also be sanded at an angle on the inside and laminated according to the above method. The strength is now fully restored.

Repairing cracks
You can easily repair cracks by making a paste of polyester laminating resin and glass fibres. Add approximately 2% hardener and the glass fibres to the polyester laminating resin base. Mix well to make a spreadable paste. Now fill the crack with the paste and spread it well. Then let it cure completely.

Step 4. Follow-up

In the steps above you have read how to carry out a polyester repair. Now that you have successfully repaired all cracks and holes, you can move on to the next step: fairing the hull with epoxy putty.

More information about a repair above the waterline?

Do you have any questions about polyester repairs or about refurbishing your boat? Our specialists are ready for you! Feel free to ask all your questions via phone, email or live chat, we are happy to help you with your project! Please check out the other informative articles we wrote on boat repair and recovery.

Product advisor
  • Expert advice
  • Superfast delivery with PostNL
  • Pay after delivery

Products used in this article

Product 1 of the 8

Boat repair and restoration

Here you can find all 32 related articles on this topic. Mis je informatie om aan de slag te gaan met jouw klus? Neem dan contact met ons op.

Gelcoat repair (cracks, scratches, dullness) Gelcoat repair (cracks, scratches, dullness)
A gelcoat finish can get damaged and (spider and hairline) cracks and scratches can occur. Fortunately, it is easy to repair and Polyestershoppen has all the ne… More information
Repairing a rotten (balsa)core Repairing a rotten (balsa)core
Many polyester sailboats have a balsa core deck covered with polyester and fibreglass. Speedboats often have a structure of trusses, made of sheet material cove… More information
Fairing the boat hull below the waterline with epoxy putty Fairing the boat hull below the waterline with epoxy putty
In this article, we explain how to fair your boat hull below the waterline after a major repair of holes and cracks. This is done easily by priming the boat. Th… More information
This is how to repair holes and cracks in your boat! This is how to repair holes and cracks in your boat!
Is your boat damaged and do you want to repair it easily? In this article we explain step by step how you can repair cracks, scratches or holes in your boat hu… More information
How to apply hard antifouling to the underwater hull How to apply hard antifouling to the underwater hull
In this article we explain how to protect the below waterline part of the boats hull with a hard antifouling from the brand International. Here we used Int… More information
Osmosis treatment in 5 steps [manual] Osmosis treatment in 5 steps [manual]
Osmosis is a nasty phenomenon and the terror for many boat owners. Unfortunately, osmosis is inevitable, but fortunately you can prevent or remedy it yourself.… More information
Repairing holes and cracks above the waterline Repairing holes and cracks above the waterline
Do you want to repair cracks, scratches or holes in your polyester boat yourself? Then quickly read this article! We are happy to explain to you what you can do… More information
Painting a boat with DD Paint [manual] Painting a boat with DD Paint [manual]
Is your boat in need of a new colour or a new paint system? In this article, we explain how to paint a hull above the waterline. We used Double Coat DD Pai… More information
Repairing boat gelcoat spider cracks Repairing boat gelcoat spider cracks
Want to repair boat gelcoat spider cracks? Small hairline cracks and spider-webbing in the polyester surface are annoying because they ruin the appearance… More information
Gelcoat repair above the waterline Gelcoat repair above the waterline
Gelcoat repair for your boat Is the gelcoat on your boat damage and do you want to repair it? No problem, you have come to the right place at Polyestershoppen.… More information
Installing boat deck fittings correctly Installing boat deck fittings correctly
Boat deck fittings can become loose over time and even cause leakage. Especially on boats with balsa decks, it is important that all fittings are installed prop… More information
Make a new floor for your boat with polyester Make a new floor for your boat with polyester
Want to repair the bottom of your polyester boat? At Polyestershoppen, you can find everything for optimal boat maintenance. From polyester to handy supplies, w… More information
Polishing your boat with Riwax! Polishing your boat with Riwax!
Over time, your boat, which used to be so beautifully shiny in the water, loses its shine due to all kinds of weather influences. The polyester or paintwork of… More information
Applying self-sharpening antifouling Applying self-sharpening antifouling
What is self-sharpening antifouling and how do you apply self-sharpening antifouling? In this article, you will read all about using self-sharpening antifouling… More information
How to quickly remove paint from steel or polyester How to quickly remove paint from steel or polyester
How do you quickly remove paint or antifouling from steel, metal or polyester? A good question because sometimes you want to tackle your boat and remove old pai… More information
Repairing boat mirror with polyester Repairing boat mirror with polyester
If the mirror in your boat is worn, damp or rotten, it is better to replace it. Fortunately, this is a job you can easily do yourself. We have written a handy s… More information
What boat paint do you need? The right paint system for your boat! What boat paint do you need? The right paint system for your boat!
What is the best boat paint? What boat paint is suitable for my boat? How do you apply a paint system? We regularly receive similar questions about painting boa… More information
Repairing cracks and holes in a polyester boat Repairing cracks and holes in a polyester boat
Do you want to repair your polyester boat? At Polyestershoppen, we know everything about optimal repair of polyester boats. We also sell all supplies. You can c… More information
Cleaning your polyester boat Cleaning your polyester boat
Are you going to refurbish a boat yourself? Then, first of all, it is important that you clean the boat properly before you continue sanding and repairing. In t… More information
Priming a boat hull with HB Coating Priming a boat hull with HB Coating
In this article, we explain step by step how to apply IJmopox HB Coating. This epoxy coating is used to protect against osmosis (polyester) and corrosion (metal… More information
Sanding your boat Sanding your boat
Do you want to sand your polyester boat? Then Polyestershoppen.nl is the place to be. Besides the fact that in our shop you will find everything to maintain you… More information
Making a boat stand Making a boat stand
In this article we will explain to you step by step how to make your own boat stand. This DIY boat stand ensures that the bottom will not be damaged when workin… More information
Applying non-skid deck coating Applying non-skid deck coating
A floor in your boat that is too slippery? Read in this article how to apply non-skid deck coating step by step so that you no longer slip. For other articles o… More information
Frequently asked questions about boat maintenance Frequently asked questions about boat maintenance
In this article, we cover the most frequently asked questions on boat maintenance. We answer questions on antifouling, primers, polishes and boat paints. For mo… More information
Applying antifouling? Read all about antifouling! Applying antifouling? Read all about antifouling!
What types of antifouling are there? And how do you apply the right antifouling to your boat? In this information article you will find everything about antifou… More information
Polishing with Dulon | Polishing polyester gelcoat Polishing with Dulon | Polishing polyester gelcoat
Have you just done a gelcoat repair or has the gelcoat of your car, boat or caravan become dull? You can easily polish a polyester gelcoat to bring back that be… More information
What boat primer do I need? All about boat primers! What boat primer do I need? All about boat primers!
What is the best primer and what primer is right for my boat? There are lots of different primers and we understand that choosing the right one can be quite tri… More information
Hempel manual on processing Silic One Hempel manual on processing Silic One
Hempel Silic One is the revolution in antifouling coatings. This biocide-free product has properties similar to those of an antifouling. However, Sili… More information
Insulating a boat with Froth-Pak Insulating a boat with Froth-Pak
Condensation on the boat hull can lead to mold. But how can you avoid condensation on the metal? This can be done by spraying a fine layer of PUR foam against… More information
All about International B-Free | Biocide-free antifouling All about International B-Free | Biocide-free antifouling
Do you want to combat underwater growth in an environmentally friendly way? Then the brand new International B-Free system is the perfect fouling release system… More information

Do you have a question?

Do you have a specific question? Call one of our specialists for free advice +3185 0220090